Conventional clamps for holding coolant hoses onto radiator tubes or nipples clamp the hose tightly around the rigid tube.
One type of clamp is a heavy spring wire which is tightened onto the hose and its ends hooked together. A second, more commonly used type of clamp, particularly for large engines used on trucks, is a stainless steel band provided with grooves or serrations that are meshed in a worm gear. By turning the worm gear, the band is circumferentially tightened. The advantage of this type of clamp is that it provides considerably circumferential adjustment.
A frequent problem with both types of clamps is that the large temperature variation between a running temperature of perhaps 200.degree. F. and freezing temperatures will cause the hose, tube and clamp to expand. Since the coefficient of expansion of the rubber or other elastomeric hose is about fifty times greater than that for the steel band, the rubber tends to be extruded out from beneath the steel band. Then, during cooling, particularly in winter temperatures down to 0.degree. F., the rubber contracts away from the tube, allowing the engine coolant to leak out of the coolant system. Not only does this result in the loss of expensive antifreeze, but if not detected, the loss of the coolant can ruin an engine in a very few seconds at its high operating temperature. When leakage is detected, the operator frequently tightens up on the adjustable type of clamp to stop the leakage. However, during the next cycle of thermal expansion and contraction, leakage may again occur. The cause of this problem is believed to be that the rubber, when it expands from beneath the steel band, loses its resiliency and ability to maintain tension on the clamp and thus seal off around the tube. Retightening of the clamp provides temporary correction but does not prevent subsequent thermal cycling from again producing leakage.